The number of different CD and DVD recorder applications is growing rapidly. Likewise, the number of media manufacturers and hence the number of different types of optical recording media is constantly increasing. It is to be expected that this situation will be the same for future optical recording formats such as BD (BluRay Disk) or HD-DVD.
The key requirement for any recording apparatus is to write data with at least a specified minimum quality, independent of the type of recording medium and the recording speed. The quality achieved during the writing process is mainly determined by the optical power control unit (OPC) and the so called write strategy used by the recording apparatus for a given optical recording medium. The optical power level is automatically adjusted by the recording apparatus, once for each new recording medium. However, the parameters for the write strategy are usually evaluated manually and determined separately for each type of recording medium and each recording speed, respectively. The parameters of the write strategy describe the shape and timing of the write signal and the write pulses, respectively. Each symbol (pit length) recorded at a certain speed has its own set of write strategy parameters on each recording medium. In total about 50 to 100 parameters need to be determined for each recording medium. The evaluation of the write strategy parameters hence needs a large amount of time and resources. Today the evaluation of the write strategy parameters for one type of recording medium engages one engineer for one day. Due to the time consuming evaluation process the number of recording media, which are supported by a recording apparatus, is limited. Similarly, new types of recording media, which arrive on the market after the development of the recoding apparatus, are not or only badly supported. This leads to customer dissatisfaction. To improve the number of supported recording media a continuously increasing amount of resources is necessary to evaluate new recording media.
Recording on recordable optical disks requires laser pulses at a high frequency. The frequency is higher than the pit frequency, as generally there are several short pulses per pit. For increased writing speeds (2×, 4×, 16×, etc.) the frequency of the laser pulses increases accordingly. This means that very high frequency signals need to be transmitted from a main processor to the laser driver. The transmission is usually performed via a flexi board, which causes problems (e.g. accuracy) for high frequencies. A known approach is to program the write strategy parameters to the pickup, i.e. the laser driver thereon, and to send only the clock and the data stream to the laser driver so that the high frequent pulses do not need to be transmitted over comparatively long flexi board wires. As it is very costly to generate the write strategy database, it is not desirable that the write strategy which is used can easily be detected by tracing the data transmission when programming the write strategy's waveform generator to the optical pickup. Furthermore, it is desirable to ensure that the write strategy programmed to the pickup is really suitable for the specific device, as a write strategy developed for a different device could lead to unreadable optical disks.